Computation of Free-surface Viscous Flows at Model and Full Scale -- a Comparison of Two Different Approaches

This paper discusses results of a workshop on freesurface viscous flow and scale effects. Participants were asked to submit computations of the viscous flow around a container ship, the 'Hamburg Test Case’, including free surface and free trim and sinkage. This paper discusses two methods that gave the most comprehensive results at this workshop, compares their results with the experimental data on model scale, and discusses the scale effects on the wave patterns and the wake fields. Computed scale effects on the resistances are compared with extrapolation methods. The two methods differ in almost every respect: one uses a steady iterative approach where the other is a time-dependent method. One method used surface fitting, finite differences, structured grids and no wall functions, where the other method uses surface capturing, finite volumes, unstructured grids and wall functions. Nevertheless, both methods give very similar results as well in the computed wave patterns as in the wake fields and the resistances. The similarity in the results and in the scale effects strongly contributes to the reliability of the computed trends.